SUPPRESSION OF MIXED LYMPHOCYTE REACTIONS BY PREGNANCY SERUM

Abstract

Maternal lymphocyte function, as assessed by stimulation with cells from a human lymphoid line, is normal in pregnancy. Maternal serum contains immunosuppressive factor(s), demonstrable by 29 wk of pregnancy and having a greater effect at 36 wk on mixed lymphocyte reactions. These immunosuppressive factor(s) block all mixed lymphocyte reactions to the same extent and are not specific towards those stimulated by paternal antigens. Anti-B cell (DR) alloantibodies, presumably directed against fetal antigens, are not uncommon in maternal serum even in early pregnancy. The presence of these antibodies in early pregnancy may be associated with selective inhibition of maternal lymphocyte stimulation by paternal antigen. No correlation was found between the presence or absence of serum suppressive factors and the clinical course of the pregnancy.